Gearbox for a hybrid vehicle, drivetrain having a gearbox of said type, and method for operating the same

Abstract

A hybrid vehicle transmission ( 1 ) having internal combustion engine ( 8 ) and electric machine ( 5 ). The transmission ( 1 ) comprises main transmission (HG) with two parallel partial transmissions; output shaft ( 4 ); first (R 1 ), second (R 2 ), third (R 3 ), fourth (R 4 ) and output constant (R 5 ) gear planes each comprising a fixed gear on countershaft (VW) and respective meshing loose gear; first (A), second (B), third (C), fourth (D), fifth (E), sixth (F), seventh (G) and eighth (H) shift elements. Whenever eighth shift element (H) is engaged, the loose gear of fifth gear plane (R 5 ) is engaged with the output shaft ( 4 ) of the main transmission (HG), whenever the seventh shift element (G) is engaged, loose gear of fourth gear plane (R 4 ) is engaged with the output shaft ( 4 ), and whenever the sixth shift element (F) is engaged, loose gear of fourth gear plane (R 4 ) is engaged with the first transmission input shaft ( 2 ).

We claim: 
     
       1. A transmission for a hybrid vehicle, wherein the hybrid vehicle has a hybrid drive with an internal combustion engine and an electric machine, the transmission comprising a housing, and the transmission further comprising at least one main transmission with at least the following assemblies:
 two partial transmissions being connected in parallel with two transmission input shafts and one output shaft, the electric machine being connectable to a first transmission input shaft of a first partial transmission of the internal combustion engine and to a second transmission input shaft of a second partial transmission; 
 a first gear plane, a second gear plane, a third gear plane, a fourth gear plane and a fifth gear serving as an output constant, each gear plane having a fixed gear fastened on a countershaft and a loose gear meshing with the respective fixed gear, supported on the first transmission input shaft or the second transmission input shaft or the output shaft; 
 a first shift element, a second shift element, a third shift element, a fourth shift element, a fifth shift element, a sixth shift element, a seventh shift element and an eighth shift element, 
 wherein whenever the eighth shift element of the main transmission is engaged, the loose gear of the fifth gear plane, which serves as the output constant, is rotationally engaged with the output shaft of the main transmission, 
 whenever the seventh shift element of the main transmission is engaged, the loose gear of the fourth gear plane, which is adjacent to the fifth gear plane which serves as the output constant, is rotationally engaged with to the output shaft of the main transmission, and 
 whenever the sixth shift element of the main transmission is engaged, the loose gear of the fourth gear plane, which is adjacent to the fifth gear plane which serves as the output constant, is rotationally engaged with the first transmission input shaft. 
 
     
     
       2. The transmission according to  claim 1 , wherein whenever the fifth shift element is engage, the first transmission input shaft is directly rotationally engaged with the output shaft of the main transmission. 
     
     
       3. The transmission according to  claim 1 , wherein
 whenever the first shift element of the main transmission is engaged, the loose gear of the first gear plane is rotationally engaged with the second transmission input shaft, 
 whenever the second shift element of the main transmission is engaged, the loose gear of the second gear plane is rotationally engaged with the second transmission input shaft, 
 whenever the third shift element of the main transmission is engaged, the first transmission input shaft and the second transmission input shaft are rotationally engaged with each other, and 
 whenever the fourth shift element of the main transmission is engaged, the loose gear of the third gear plane is rotationally engaged with the first transmission input shaft. 
 
     
     
       4. The transmission according to  claim 1 , wherein the first shift element and the second shift element of the main transmission are formed as a first double shift element,
 the third shift element and the fourth shift element of the main transmission are formed as a second double shift element, 
 the fifth shift element and the sixth shift element of the main transmission are formed as a third double shift element, 
 in a region of each of the double shift elements only one of the shift elements is always engaged or both shift elements of the respective double shift elements are disengaged. 
 
     
     
       5. The transmission according to  claim 1 , wherein the electric machine of the hybrid drive interconnection of an input planetary transmission can be rotationally engaged with the second transmission input shaft of the main transmission, or
 the electric machine of the hybrid drive can be directly rotationally engaged with the second transmission input shaft of the main transmission. 
 
     
     
       6. The transmission according to  claim 5 , wherein the input planetary transmission, located between the electric machine of the hybrid drive and the second transmission input shaft of the main transmission, has planetary elements which comprise a sun gear, a ring gear and a planetary carrier carrying planets,
 a first element of the input planetary transmission is permanently rotationally engaged with the second transmission input shaft of the main transmission; a second element of the input planetary transmission is permanently rotationally engaged with the electric machine, and 
 a third element of the input planetary transmission is either permanently connected to the housing, or whenever a first shift element interacting with the first planetary transmission is engaged, is connected to the housing and, whenever a second shift element interacting with the input planetary transmission is engaged, is rotationally engaged with the first transmission input shaft of the main transmission. 
 
     
     
       7. The transmission according to  claim 6 , wherein the first and second shift elements, which interact with the input planetary transmission, are formed by a sixth double shift element, and only one of the shift elements of the sixth double shift elements is always engaged or both shift elements of the sixth double shift elements are disengaged. 
     
     
       8. The transmission according to  claim 1 , wherein a range group with an output planetary transmission and three shift elements are arranged downstream from the main transmission,
 the output planetary transmission of the range group has planetary elements which comprise a sun gear, a ring gear and a planetary carrier carrying planets, 
 a first element of the output planetary transmission of the range group is permanently rotationally engaged with the output shaft of the main transmission, and 
 a second element of the planetary transmission of the range group is permanently rotationally engaged with an output shaft of the range group, 
 whenever a first shift element of the range group is engaged, the loose gear of the fifth gear plane, which serves as the output constant, is rotationally engaged with the output shaft of the range group, 
 whenever a second shift element of the range group is engaged, a third element of the output planetary transmission is connected to the housing, 
 whenever a third shift element of the range group is engaged, the third element of the planetary transmission is connected rotationally engaged with the output shaft of the range group. 
 
     
     
       9. The transmission according to  claim 8 , wherein
 the seventh shift element and the eighth shift element of the main transmission are formed by a fourth double shift element, and the first shift element of the range group is configured as a single shift element, or 
 the seventh shift element of the main transmission is s single shift element and the eighth shift element of the main transmission and the first shift element of the range group are formed by a fourth double shift element, 
 wherein only one of the shift elements of the fourth double shift elements is always engaged or both shift elements of the fourth double shift elements are disengaged. 
 
     
     
       10. The transmission according to  claim 8 , wherein the second shift element and the third shift element of the range group are formed by a fifth double shift element, wherein only one of the shift elements of the fifth double shift element is engaged or both shift elements of the fifth double shift element are disengaged. 
     
     
       11. The transmission according to  claim 1 , wherein the main transmission is provided with a reverse gear plane by which a mechanical reverse gear can be realized. 
     
     
       12. A drive train for a hybrid vehicle, with a hybrid drive having an internal combustion engine and an electric machine and with a transmission according to  claim 1 . 
     
     
       13. The drive train according to  claim 12 , wherein the internal combustion engine is permanently coupled or releasably coupled, by a separating clutch, to the first transmission input shaft. 
     
     
       14. The method according to  claim 13 , wherein after disengaging the fifth shift element of the main transmission,
 shifting the range group by disengaging the second shift element of the range group and by engaging the third shift element of the range group. 
 
     
     
       15. A method for operating a drive train of a hybrid vehicle according to  claim 12 , for executing a gear change in an ISG operating mode, in which the third element of the planetary transmission, shifted between the electric machine of the hybrid drive and the second transmission input shaft of the main transmission, is connected to the housing, of a temporally highest gear when the second shift element of the range group is engaged in a highest gear when the second shift element of the range group is engaged, with the following steps:
 first uncoupling the loose gear of the output constant of the output shaft of the main transmission by a load free disengagement of the eighth shift element of the main transmission, 
 actively synchroning the first shift element of the range group via the electric machine, 
 then engaging the first shift element of the range group and the second shift element of the main transmission is disengaged load free, 
 then actively synchronizing and engaging the first shift element of the main transmission via the electric machine, 
 then setting the internal combustion engine load free and disengaging the fifth shift element of the main transmission load free, and 
 then actively synchronizing and engaging the third shift element of the main transmission via the internal combustion engine. 
 
     
     
       16. A method for operating a drive train of a hybrid vehicle according to  claim 12  for executing a gear change in an EDA operating mode, in which the third element of the input planetary transmission, connected between the electric machine of the hybrid drive and the second transmission input shaft of the main transmission, is connected rotationally engaged with the first transmission input shaft, of a temporally highest gear when the second shift element of the range group is engaged in a highest gear when the second shift element of the range group is engaged, comprising:
 first uncoupling the loose gear of the output constant of the output shaft of the main transmission by a load free disengaging of the eighth shift element of the main transmission, 
 then actively synchronizing the first shift element of the range group via the electric machine, 
 then engaging the first shift element of the range group and disengaging the second shift element of the main transmission in a load free state, 
 then actively synchronizing and engaging the first shift element of the main transmission via the electric machine, 
 then setting torque provided by the internal combustion engine and the electrical machine such that the same are in proportion to a stationary transmission ratio of the input planetary transmission, which is shifted between the electric machine and the second transmission input shaft, as a result of which the fifth shift element of the main transmission is set load free and is disengaged load free, 
 then actively synchronizing and engaging the third shift element of the main transmission via the internal combustion engine and the electric machine. 
 
     
     
       17. The method according to  claim 16 , wherein after disengaging of the fifth shift element of the main transmission, shifting the range group by disengaging the second shift element of the range group and engaging the third shift element of the range group.